TWI818327B - Coating composition and base material with coating film - Google Patents

Abstract

The main subject of the present invention is to provide a coating liquid containing polymer coatings, inks, adhesives, positive electrodes, negative electrodes, separators, etc. of lithium ion batteries, which can form an easy-drying coating material on the construction surface. . The solution of the present invention is a coating composition, which is a composition including a filler, a binder, a tackifier, and a solvent. The characteristic is that the aforementioned binder is selected from the group consisting of diene rubber and (meth)acrylate polymerization. At least one of the substances, the viscosity of the coating composition measured at a shear speed of 0.01/s is 1.0×10 ⁶ Pa･s or less, and the following thixotropy index (TI) is 1.1×10 ⁶ or more; [Thixotropic Index (TI)] = [Viscosity of the coating composition measured at a shear speed of 0.01/s]/[Viscosity of the coating composition measured at a shear speed of 10000/s].

Description

Coating composition and base material with coating film

The present invention relates to compositions containing fillers, binders and tackifiers. It mainly relates to coatings, inks, adhesives, positive electrodes, negative electrodes, separators of lithium-ion batteries, etc. containing polymers, which can be formed on the construction surface. A composition of easy-drying paint.

In the industrial field, coating and printing technologies using compositions are widely used from the perspective of environmental aspects, safety aspects, or efficiency. In such a printing technology, it is desired to have so-called high coating properties that can discharge and apply the minimum necessary composition at high speed and high precision, and the resulting coating surface is smooth.

However, the physical properties of the composition with excellent coating properties cannot be controlled. For example, Patent Document 1 discloses that a battery separator excellent in dispersibility and ease of painting can be obtained by setting a suspension of fibrous cellulose diluted with ion-exchange water to a specific thixotropic index (TI). Coating fluid.

Patent Document 2 discloses a coating liquid for metal ion secondary battery separators that can form a uniform coating film with excellent coatability by setting the viscosity ratio at a designated shear speed to be a specific or higher. [Prior technical literature] [Patent Document]

[Patent Document 1] International Publication No. 2018/070473 [Patent Document 2] Japanese Patent No. 5829557

[Problem to be solved by the invention]

However, Patent Document 1 does not disclose a TI in a state containing a composition other than fibrous cellulose and ion-exchanged water. Furthermore, high-speed coating properties are not stated or implied. Patent Document 2 states that when the content of water-soluble components in the coating liquid is 5% by mass or less, the coating liquid has an extremely large solid content, and there is no disclosure at all from the viewpoint of high-speed coating properties or surface smoothness. .

Although many compositions have good paintability, the characteristics that contribute to high-speed paintability or surface smoothness are not clear. [Means used to solve problems]

Under this situation, as a result of diligent research, the inventors found that by using a composition with a viscosity ratio between high shear speed and low shear speed in a specific range, a coating liquid with excellent coating properties can be obtained. The coating film with excellent surface smoothness can be fully used for the above-mentioned purposes, and finally the present invention is completed.

That is, the structure of this invention is as follows. [1] A coating composition, which is a coating composition including a filler, a binder, a tackifier, and a solvent, characterized in that the aforementioned binder is selected from the group consisting of diene rubber and (meth)acrylate polymerization At least one of the substances, the viscosity of the coating composition measured at a shear speed of 0.01/s is 1.0×10 ⁶ Pa·s or less, and the following thixotropic index (TI) is 1.1×10 ⁶ or more; [Thixotropic index (TI)]=[The viscosity of the coating composition measured at a shear speed of 0.01/s]/[The viscosity of the coating composition measured at a shear speed of 10000/s]. [2] The coating composition of [1], wherein the ratio of the filler to the tackifier is 10 to 100 in terms of mass ratio (filler/tackifier). [3] The coating composition of [1] or [2], wherein the aforementioned tackifier is polyN-vinylcarboxylic acid amide. [4] The coating composition according to [1] to [3], wherein the aforementioned tackifier is polyN-vinyl acetamide. [5] The coating composition according to [1] or [2], wherein the aforementioned tackifier is polyvinylpyrrolidone. [6] The coating composition of [1] to [5], which contains water as a solvent. [7] The coating composition according to [1] to [6], wherein the thixotropic index (TI) value is 1.1×10 ⁸ or less. [8] The coating composition according to [1] to [7], wherein the aspect ratio of the filler is 1 or more and less than 2. [9] A base material with a coating film, which includes a coating film formed of the coating compositions of [1] to [8] and a base material. [10] A separator formed of a base material coated with a technical film as in [9]. [11] A secondary battery using the separator of [10]. [12] A lithium ion secondary battery using the separator of [10]. [13] An electrode material having a coating film formed of the coating composition of [1] to [8] on the surface of a substrate. [Effects of the invention]

When the coating composition of the present invention is applied at high speed and with high precision, a smooth coating film on the coating surface can be obtained. If such technology is used in the formation of electrodes or separators for secondary batteries, especially lithium-ion secondary batteries, the production efficiency of secondary batteries can be improved.

Hereinafter, embodiments for carrying out the present invention will be described. [Coating composition] The coating composition of this embodiment includes fillers, tackifiers, adhesives, and solvents.

The viscosity of such a coating composition measured at a shear speed of 0.01/s is 1.0×10 ⁶ Pa·s or less. The following thixotropic index (TI) is 1.1×10 ⁶ or more, preferably 3.0×10 ⁶ or more, more preferably 1.0×10 ⁷ or more. Moreover, the thixotropic index (TI) is preferably 1.1×10 ⁸ or less, more preferably 5.0×10 ⁷ or less. Such a specified thixotropic index (TI) can be adjusted by the aforementioned composition.

[Thixotropic Index (TI)] = [Viscosity of the coating composition measured at a shear speed of 0.01/s]/[Viscosity of the coating composition measured at a shear speed of 10000/s]. The thixotropic index (TI) in the present invention is the ratio of the viscosity at high shear speed to the viscosity at low shear speed. With this ratio in the specified range, even high-speed and high-precision coating can be achieved. Even in this case, there will be no streaks or flow on the surface, and an extremely smooth coating can be obtained. [filler] As fillers, those composed of inorganic substances are used. Specifically, preferred fillers are alumina, boehmite, talc, kaolin calcium carbonate, calcium phosphate, amorphous silica, crystalline glass filler, titanium dioxide, and silica-alumina composite oxide. Particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, etc. Among them, alumina and boehmite are more preferred.

The shape of the filler is not particularly limited. In addition to spherical, polyhedral, plate, scaly, columnar, and tubular shapes, the filler may also be fibrous. The aspect ratio of the filler is preferably in the range of 1 to 15, more preferably in the range of 1 to less than 2. The aspect ratio of the filler is preferably from 1 to 15 because it is easy to mix with other components in the coating composition.

The 50% particle diameter D50 of the cumulative particle size distribution based on the volume of the filler is preferably in the range of 0.1 to 50 μm, more preferably in the range of 0.5 to 10 μm. [Tackifier] Tackifiers are composed of organic polymers. The binder mentioned below is not included in the tackifier. Preferred tackifiers include polyN-vinylcarboxylic acid amide, polyN-vinylpyrrolidone, sodium salt of carboxymethylcellulose, polyacrylamide, polyvinyl alcohol, carrageenan, and xanthan Polysaccharides such as gum, guar gum, pectin, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylethylhydroxycellulose, methylcellulose, hydroxypropylfiber Cellulose-based polymers such as cellulose, and ammonium salts and alkali metal salts of these cellulose-based polymers.

Among them, polyN-vinyl carboxylic acid amide or polyN-vinyl pyrrolidone is preferred, polyN-vinyl carboxylic acid amide is more preferred, and polyN-vinyl acetamide is still more preferred. Specific examples of the monomer constituting polyN-vinylcarboxylic acid amide include N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, and N-vinylbenzylamine. Amide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethyl Acetamide, etc. Among them, N-vinyl acetamide is particularly preferred.

These may be individual polymers or copolymers. During copolymerization, it is not particularly limited as long as salts of itaconic acid, maleic acid, crotonic acid, (meth)acrylic acid, etc. can also be copolymerized.

The component derived from N-vinyl acetamide in the polyN-vinylcarboxylic acid amide is preferably 60 mol% or more. The viscosity of the tackifier is based on the original viscosity (without adjusting the solution concentration), and is preferably between 30mPa·s and below 30000mPa·s. This range is preferable because it is easier to apply. [Binder] The adhesive contains at least one selected from the group consisting of diene rubber and (meth)acrylate polymer, and more preferably consists of only at least one selected from the group consisting of diene rubber and (meth)acrylate polymer. Examples of diene rubber include styrene-butadiene rubber, butyl rubber, butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, ethylene propylene diene rubber, or modified products thereof. (Meth)acrylate polymer refers to a polymer containing at least one of acrylate and methacrylate. (Meth)acrylate polymers can be copolymerized and contain more than 50 mol% of acrylate and methacrylate.

Other monomers contained in the (meth)acrylate polymer are not particularly limited as long as they can be copolymerized with the (meth)acrylate. These can be added to the coating material in the form of emulsion latex dispersed in water.

In addition, polyvinyl alcohol, poly(meth)acrylic acid, higher alcohol ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, etc. can also be used as a binder. When poly(meth)acrylic acid is used, Although the salt is not particularly limited, an ammonium salt that does not contain metal is preferred, and for example, ammonium polyacrylate can be used.

Among them, cross-linked acrylic emulsion is preferred. The acrylic emulsion can be a single polymer or a copolymer, either one is acceptable. In addition, the emulsion can be used directly or can be used after solidification. [Solvent] The solvent is not particularly limited as long as it disperses or dissolves the above components and does not react. However, in view of drying properties, a volatile solvent is used. Specifically, although water or a polar solvent compatible with water is used, it is preferable that water contains 50 mass % or more, and it is more preferable that water alone is used. The preferred water is ion-exchange water. Examples of solvents other than water include alcohols such as methanol, ethanol, and isopropyl alcohol. [Dispersant] The coating composition of the present invention may contain a dispersant if necessary. The dispersing agent is not particularly limited when dispersing the filler, but is preferably a fatty acid ester of dodecyl benzene sulfonic acid, sorbitol, and sorbitan anhydride. The salt is not particularly limited, but an ammonium salt that does not contain metal is preferred. [Composition and preparation method of coating composition] The ratio of filler to tackifier in the coating composition is preferably 10 to 100, more preferably 20 to 80, and still more preferably 30 to 60 in terms of mass ratio (filler/tackifier). This ratio is preferable because the coating process is easy, the drying property is good, and the coating layer obtains sufficient strength.

The quality of the filler in the coating composition is preferably in the range of 10 to 80% by mass, more preferably in the range of 20 to 50% by mass. Based on the solid content in the coating composition, the mass of the filler is preferably in the range of 50 to 99 mass %, more preferably in the range of 70 to 98 mass %.

The solid content of the binder is preferably in the range of 0.1 to 20 mass %, more preferably 1 to 5 mass % relative to the mass of the filler. The mass of the binder (solid content) in the coating composition is preferably in the range of 0.1 to 20 mass %, more preferably in the range of 1.0 to 5.0 mass %. Taking the solid content in the coating composition as a basis, the mass of the binder (solid content) is preferably in the range of 0.2 to 10% by mass, more preferably in the range of 0.5 to 5.0% by mass.

The mass of the tackifier in the coating composition is preferably in the range of 0.01 to 20 mass%, more preferably in the range of 1.0 to 5.0 mass%. Taking the solid content in the coating composition as a basis, the mass of the tackifier is preferably in the range of 0.2 to 10% by mass, more preferably in the range of 0.5 to 5% by mass.

The solvent such as water is usually 0.1 to 1000 parts by mass, and more preferably 1 to 200 parts by mass relative to 100 parts by mass of the solvent. In this range, good fluidity of the coating composition can be obtained, and a coating composition with a viscosity of 1.0×10 ⁶ Pa·s or less measured at a shear speed of 0.01/s can be obtained.

When a dispersant is included, its amount is preferably in the range of 0.01 to 10% by mass, more preferably 0.1 to 5% by mass in the coating composition. When included in this range, the dispersibility of the filler can be improved.

Although the mixing method of each component of the coating composition is not particularly limited, in order to achieve a more uniform mixing state, it is preferable to dissolve or disperse the binder, tackifier, etc. in the solvent, and then add and mix the filler. Furthermore, it is more preferable to use a solution in which the binder, thickener, etc. are dissolved or dispersed while stirring continuously, while the filler is added one after another and stirred to mix and homogenize. This makes it possible to obtain an ideal mixed form. [use] The coating composition of this embodiment can be used in various coating liquids such as coatings, inks, adhesives, positive electrodes, negative electrodes, separators of lithium ion batteries, etc., depending on the type of filler blended.

Although the coating composition can be used directly as a coating fluid, if necessary, the concentration or viscosity can be appropriately adjusted with a solvent, etc., and used as a coating fluid. For example, a coating film is produced by coating the coating composition on the surface of a substrate and drying it. Alternatively, a coating film composed of a coating composition may be provided on the surface of a base material (called a base material with a coating film) to serve as an electrode material.

Since the coating composition of the present invention contains fillers, binders, tackifiers, and solvents, the viscosity of the coating composition measured at a shear speed of 0.01/s is 1.0×10 ⁶ Pa·s or less, and the following thixotropy The index (TI) is 1.1×10 ⁶ or more. Even if the coating composition is applied at high speed and with high precision, a smooth coating film on the coating surface can be obtained.

Although the coating method of the base material of the coating composition is not particularly limited, in addition to spray coating, roller coating, rod coating, gravure coating, slot die coating, knife coating, inkjet coating, or brush coating, In addition to dip coating, a roll-to-roll pattern coating device can also be used for continuous coating.

Furthermore, the coating composition may include known materials added to the coating in addition to the above. For example, surface conditioners, defoaming agents, leveling agents, pigments, dyes, etc. may be included.

As the base material, films, nonwoven fabrics, porous bodies, plate-shaped bodies, etc. can be used without particular limitation. Examples of materials constituting the base material include ethylene alone or a copolymer with other α-olefins, homopolypropylene, a copolymer of propylene and other olefins, polyethylene terephthalate, and polyethylene naphthalate. Ester, polyamide ether ketone, polyimide, polyamide, polyphenylene sulfide, polyphenylene ether, polyethylene, polyether styrene, polyether ether ketone, polybenzimidazole, polyether ether ketone Organic resin materials such as amines, polyamide imides, poly(p-phenylene-2,6-benzobisoxazole), fluororesins, epoxy resins, and metals such as aluminum, copper, silver, iron, etc. Materials, glass (silicon oxide), alumina, magnesium oxide, aluminum nitride, aluminum carbide, silicon nitride, barium titanate and other inorganic materials. One type of base material may be used alone, or two or more types may be used in combination. Among them, the base material is preferably polyolefin, more preferably at least one selected from polyethylene and polypropylene, and most preferably a three-layer laminate laminated in the order of polypropylene/polyethylene/polypropylene. When a porous base material made of such a material is used, it can be used as a secondary battery separator or the like.

When the porous base material is a polyolefin film, it may be produced by a wet method or a dry method, and is not particularly limited. In addition, when the porous base material is composed of a three-layer laminate, it is preferable that all three layers are produced by a dry process. Those having such a structure have no curling and have good heat resistance, mechanical strength, etc.

Furthermore, the so-called dry method refers to a dry process that does not use solvents when producing films. Examples include melt molding or injection molding of molten resin through a T-shaped mold. In addition, the outer layer and the inner layer can be made by a dry method or a wet method. The wet method is a method in which a resin with additives added and mixed is used to form a film, and then the solvent extracts the additives to form gaps.

The thickness of the entire base material can be appropriately selected depending on the purpose of mechanical strength, performance, miniaturization, etc., but is preferably 7.0 μm or more, and the upper limit is preferably 50 μm or less. When the thickness is within this range, the strength can be increased.

Moreover, in the case of a porous base material, the air permeability measured in accordance with JIS P 8117:2009 is preferably 80 seconds/100ml or more, and the upper limit is preferably 700 seconds/100ml or less. When the air permeability is within this range, short circuiting is difficult and the mobility of ions is high.

The porosity of the porous base material is preferably 30% or more, and the upper limit is preferably 70% or less. If the porosity is within this range, the mechanical strength will be high, short circuit will not occur, and the mobility of ions will also be improved.

The maximum pore diameter of the porous base material is preferably 0.05 μm or more, and the upper limit is preferably 2 μm or less. When this range is used as a separator, the mobility of ions is high and the resistance is greatly reduced.

The thickness of the coating film is not particularly limited. A coating film with a thickness of 0.5 to 20 μm is acceptable, but is not particularly limited. The drying method of the coating film is not particularly limited, and examples include spin drying, vacuum drying, warm air drying, infrared drying, etc. The drying time is not particularly limited either.

When constituting the separator, the coating composition may be coated on the surface of the base material. When constituting the electrode, the above-mentioned coating composition can be mixed with the positive electrode active material or the negative electrode active material and coated on the surface of the above-mentioned base material or the surface of the current collector, or the method of mixing the positive electrode active material or the negative electrode active material can be used. Or both of them are coated on the electrode foil, or a thin film coating composition is inserted into the surface of the positive electrode or negative electrode or both of the current collectors to form the battery electrode.

The components constituting a lithium-ion secondary battery can be roughly divided into positive electrodes, negative electrodes, separators, and electrolytes. The positive electrode and the negative electrode respectively contain active materials that perform oxidation/reduction reactions that send out and accept electrons. The positive electrode and the negative electrode can be used in the form of an electrode group of a laminated structure laminated with a battery separator, or in the form of an electrode group of a winding structure in which the separators are laminated.

The positive electrode is not particularly limited as long as it is used in a conventionally known lithium ion secondary battery. The positive electrode contains active materials that can absorb and release Li ⁺ ions. The negative electrode is not particularly limited as long as it is used in a conventionally known lithium ion secondary battery. The negative electrode contains active materials that can absorb and release Li ⁺ ions.

The positive electrode and the negative electrode can be used in the form of an electrode group with a laminated structure laminated through a separator, or in the form of an electrode group with a winding structure wound around the same. As the electrolyte, a solution in which a lithium salt is dissolved in an organic solvent is used. The lithium salt is not particularly limited as long as it dissociates in the solvent to form Li ⁺ ions and does not cause side reactions such as decomposition in the voltage range used as a battery. The organic solvent is not particularly limited as long as it dissolves the lithium salt and does not cause side reactions such as decomposition in the voltage range used as a battery.

Each component produced using the coating composition of this embodiment can be suitably used in each component of the battery mentioned above. In addition to power supplies for mobile devices such as mobile phones and laptop computers, electric vehicles, hybrid vehicles, electric motorcycles, electric-assisted bicycles, power tools, razors, etc., lithium-ion batteries can also be used in Various uses known from the past. [Example]

Hereinafter, although the present invention will be described using Examples, the present invention is not limited to these Examples. [Examples 1 to 12, Comparative Examples 1 to 3] In a 200ml resin container, measure the prescribed amounts listed in Table 1 in the order of ion exchange water, surfactant, dispersant, binder, tackifier, and inorganic filler, and put it into a rotational revolution type kneader (ARE-made by THINKY Co., Ltd. 250). Perform sealing and mix under conditions of mixing for 60 seconds and defoaming for 60 seconds to obtain a uniform coating composition.

A polypropylene sheet (thickness: 1 mm) was fixed on the coating table of the coating machine, and 3.5 g of the obtained coating composition was applied using a bar coater (width: 50 mm × thickness: 5 μm, manufactured by YOSHIMITSU Seiki Co., Ltd.), and the coating was automatically A working machine (Pi-1210 manufactured by TESTER Industrial Co., Ltd.) was used to coat the film into a width of 15 cm and a length of 30 cm at a speed of 200 mm/second.

Then, the polypropylene sheet forming the coated object was dried in a warm air dryer at a temperature of 40° C. for 1 hour to obtain a coated sheet. Each component used in the composition is as follows.・Filler alumina: AL160-SG-3 (manufactured by Showa Denko Co., Ltd.) D ₅₀ : 0.52 μm, aspect ratio 1.4 Flake boehmite: Cerasur (manufactured by Kawai Lime Industry Co., Ltd.) Aspect ratio: 20 to 40 Flake alumina: Cerasurα (manufactured by Kawai Lime Industry Co., Ltd.) Aspect ratio: 20 to 40 ・Binder acrylic emulsion: Polysol (registered trademark) LB-350 (manufactured by Showa Denko Co., Ltd.) SBR (styrene) Butadiene rubber aqueous dispersion): BM400B (manufactured by Japan ZEON Co., Ltd.) Ammonium polyacrylate: ARON (registered trademark) A-30SL (manufactured by Toa Gosei Co., Ltd.) ・Tackifier poly-N-vinyl acetate Amine PNVA (registered trademark)-1: GE191-043 (manufactured by Showa Denko Co., Ltd.), original viscosity 5000 mPa·s, solid content 4 mass% Poly-N-vinyl acetamide PNVA (registered trademark)-2: GE191-104 (Showa Denko Co., Ltd.), original viscosity 18000 mPa·s, solid content 10% by mass Poly-N-vinyl acetamide PNVA (registered trademark)-3: GE191-107 (Showa Denko Co., Ltd.) ), original viscosity 50 mPa・s, solid content 10 mass% Carboxymethylcellulose CMC-Na: MAC350HC (manufactured by Nippon Paper Co., Ltd., 2 mass% viscosity 7800mPa・s) Polyvinylpyrrolidone: PVP K-90 (Manufactured by Tokyo Chemical Industry Co., Ltd.) ・Dispersant sodium dodecylbenzene sulfonate aqueous dispersion: NEOPELEXG-65 (manufactured by Kao Co., Ltd.)

The obtained compositions and coated sheets were evaluated as follows.

<Rotational viscosity>

Use Brookfield's DV2T viscometer Spindle SC4-28 with a small sample adapter with water jacket, put 20g of the coating composition into the sample holder, and measure the rotational viscosity at a rotation speed of 0.3 rpm and 100 rpm.

<Solution viscosity>

The coating composition was evaluated on a B-type viscometer (DV2T type viscometer Spindle SC4-28 with water jacket made by Brookfield Company, small sample adapter) at 23°C and 50 rpm.

However, data will not be measured in the blank columns of Examples 8 to 12.

<Shear viscosity, TI>

TI (Thixotropy‧Index) is calculated by the following formula.

TI = viscosity of the coating composition at a shear speed of 0.01/s (Pa‧s) ÷ viscosity of the coating composition at a shear speed of 10000/s (Pa‧s)

The shear viscosity was measured using a rotary viscometer made by Anton Parr. Specifically, the viscosity of the coating composition at 23°C was measured while increasing the speed from the shear speed of 0.01sec ^-1 to 10000sec ^-1 over 400 seconds, and continuously from 10000sec ^-1 to 0.01sec ^-1 over 400 seconds. Measure while reducing the speed. The measured value when measuring while reducing the shear speed was defined as the viscosity at each shear speed.

＜Viscosity of carboxymethylcellulose＞ Carboxymethylcellulose was adjusted with water so that the solid content became 2% by mass, and DVE type viscometer Spindle H04 was manufactured by Brookfield Corporation, and was evaluated at 23° C. and 50 rpm. ＜Coater film thickness＞ Use the pressure thickness measuring device PF-11J manufactured by TECLOCK to measure the center of the dry film and two points separated by 10cm from the center to the top and bottom, totaling three points, and average them. ＜Appearance of coated surface＞ The surface appearance of the coated sheet was judged based on the following criteria. 〇: No voids were confirmed on the painted surface △: Within 10 gaps are confirmed on the painted surface ×: More than 10 voids were confirmed on the painted surface ＜Surface roughness＞ Using a Surtronic Duo surface roughness meter (manufactured by TAYLOR HOBSON), the center of the coated sheet (15cm×30cm) and two points separated by 10cm from the center to the top and bottom, totaling three points, were measured for arithmetic mean roughness (Ra) and averaged. ＜Strip Evaluation＞ A cellophane tape peeling test was performed on the coated surface of the coated sheet using a 15mm wide cellophane tape made by NICHIBAN, and the adhesion between the coated object and the polypropylene sheet was evaluated in the following three stages. ○: The painted part is not peeled off. △: Although the painted part is slightly peeled off, it is still practical. ×: Part of the coating is peeled off, which is not allowed for practical purposes ＜Heat resistance evaluation＞ From the coated sheet, peel off the coated object to a certain portion with a thickness (6 to 7 μm), take a rectangular shape (5cm x 4cm), and measure the lengths of the four sides. Next, the test pieces were placed on metal rods at a distance that did not interfere with each other and allowed to stand.

Put the metal rod into a wind furnace with an internal temperature of 150°C and let it stand for 15 minutes. Take it out and measure the dimensions of the four sides. Put the test piece after the measurement into the air furnace adjusted to 200°C again, let it stand for 15 minutes, take it out, and measure the dimensions of the four sides.

Use the following items to evaluate. 〇: The shrinkage rate is 20% or less at all sides between 150°C and 200°C. △: In the 150℃ and 200℃ tests, the shrinkage rate exceeds 20% and is less than 30% on any side, and the shrinkage rate of all sides is 30% or less. ×: The shrinkage rate exceeds 30% in either 150℃ or 200℃ test.

＜Aspect Ratio＞ According to JIS R1670-2006, measure the long diameter and short side of 100 particles in a microscope photo, average the length, and calculate it by averaging the long diameter ÷ the average short side. <D ₅₀ > The volume distribution reference median diameter (hereinafter sometimes referred to as D ₅₀ ), the volume average diameter of the volume distribution standard.

From Table 2, it can be seen that in the embodiments where the TI is within a specific range, a coating film with no disorder on the coating surface, high surface smoothness, and excellent peelability or heat resistance can be formed.

Claims (14)

A coating composition, which is a coating composition including fillers, binders, tackifiers, and solvents, characterized in that the aforementioned binders include diene rubbers and (meth)acrylate polymers. At least one, the viscosity of the coating composition measured at a shear speed of 0.01/s is 1.0×10 ⁶ Pa‧s or less, the mass of the filler in the aforementioned coating composition is 10~80% by mass, and the following thixotropic index (TI) is 1.1×10 ⁶ or more; [Thixotropic Index (TI)] = [Viscosity of the coating composition measured at a shear speed of 0.01/s] / [Viscosity of the coating composition measured at a shear speed of 10000/s viscosity of the substance]. Such as the coating composition of claim 1, wherein the ratio of the aforementioned filler to the aforementioned tackifier is 10 to 100 in terms of mass ratio (filler/tackifier). The coating composition of claim 1 or 2, wherein the aforementioned tackifier is polyN-vinylcarboxylic acid amide. The coating composition of claim 1 or 2, wherein the aforementioned tackifier is polyN-vinyl acetamide. The coating composition of claim 1 or 2, wherein the aforementioned tackifier is polyvinylpyrrolidone. Such as the coating composition of claim 1 or 2, which contains water as a solvent. The coating composition of claim 1 or 2, wherein the value of the aforementioned thixotropic index (TI) is 1.1×10 ⁸ or less. For example, the coating composition of claim 1 or 2, wherein the former The aspect ratio of the filler is more than 1 and less than 2. For example, the coating composition of claim 1 or 2, wherein the solid content of the aforementioned binder is 0.1 to 20 mass% relative to the mass of the aforementioned filler, and the mass of the aforementioned binder (solid content) in the aforementioned coating composition The mass of the aforementioned tackifier in the aforementioned coating composition is 0.01 to 20 mass %, and the aforementioned filler is 0.1 to 1000 mass parts relative to 100 mass parts of the aforementioned solvent. A base material with a coating film, which includes a coating film and a base material formed by a coating composition according to any one of claims 1 to 9. A separator formed by a base material with a coating film as claimed in claim 10. A secondary battery using the separator of claim 11. A lithium ion secondary battery using the separator of claim 11. An electrode material is formed by having a coating film formed of the coating composition according to any one of claims 1 to 9 on the surface of a base material.